1) the 2300AD csv would be great. I pulled your various star map files from your site, and I think a few of your 2300 reference stars are missing from that data.

2) Wondering about current star data vs. what's still undiscovered. If I look at a display of all the stars near earth, there are some big empty gaps, such as between Earth and 61 Cygni. How likely is it that there are a few undiscovered M dwarfs in that direction? I assume we'll keep discovering new brown dwarfs by the truckload, but how many red dwarfs might be lurking still within say 20 ly?

3) wikipedia keeps a list of nearby stars. Is there a good place to go with more current data that's easily accessible?

2) Wondering about current star data vs. what's still undiscovered. If I look at a display of all the stars near earth, there are some big empty gaps, such as between Earth and 61 Cygni. How likely is it that there are a few undiscovered M dwarfs in that direction? I assume we'll keep discovering new brown dwarfs by the truckload, but how many red dwarfs might be lurking still within say 20 ly?

That depends how dim an object you're prepared to consider. The Tycho-2 catalogue, based on Hipparcos data, is 99% complete to magnitude 11 and 90% complete to magnitude 11.5, but for an M9 with luminosity of 0.00015 L☉ I reckon that that is only 2 pc — 6.5 light-years or so. GAIA data will be a lot more complete. I think, though I am not confident that I am calculating the right things because the magnitude scale confuses me, that it ought to be 99% complete for M9 and brighter out to 126 parsecs, and published next year.

Quote:

3) wikipedia keeps a list of nearby stars. Is there a good place to go with more current data that's easily accessible?

I don't know how easily accessible the GAIA data published so far is. There's an overwhelming amount of it and I think it is lacking any identifiers that would allow you to identify its data points with entries in any other catalogue. Also, the data published so far (last September) are preliminary and I don't know what they are missing.

The AllWISE catalog has a limiting magnitude around 16 in the near infrared. It should spot an M5 dwarf (actually the dimmest in those bands) out to 191 pc.

Quote:

I don't know how easily accessible the GAIA data published so far is. There's an overwhelming amount of it and I think it is lacking any identifiers that would allow you to identify its data points with entries in any other catalogue. Also, the data published so far (last September) are preliminary and I don't know what they are missing.

The Gaia* Data Release 1 (DR1) catalog is available from the VizieR catalog service ( http://vizier.u-strasbg.fr/ ), along with AllWISE and a plethora of others. DR1 includes astrometry and G-band photometry for 1.1 billion sources, but no proper motion data or spectroscopy. There is also a hybrid Tycho-Gaia catalog that gives distances and proper motions for objects in the Tycho catalog, based on the differences between the two.

VizieR lets you search multiple catalogs by position, with an accuracy you specify. There is a tool called TOPCAT (Tool for OPerations on Catalogues And Tables, http://www.star.bris.ac.uk/%7Embt/topcat/) that I haven't played with yet, but is supposed to let you search and manipulate even extremely large catalogs in near real time.

I recently found some 2D hex maps I had drawn in Sep 2000. While searching around for ideas, I found this little gem on the Traveller® Wiki:

1) The star's longitude angle (θ) is within a 45o bearing-arc between the "true" coordinate axes and the Traveller Charted Space Map coordinate axes, and

ISTR from my experiments 20-some years ago that it was more like 90° counter-clockwise. Does anyone else have experience with this?

2) The star's assigned distance from Terra on the hexmap falls somewhere between its true distance R in parsecs, and its 2D-projection onto the flat map as seen from above, found by Dproj = {R * cos(ɸ)}, where (ɸ) is the latitude angle. If desired, the distance above/below the plane can be determined by Z = {R * sin(ɸ)}

Does anyone know who wrote ths? Has anyone used it?

My trig is a bit rusty. I'm not getting why this would be valid, or why he'd want to use it. IIRC the cos of 0 is 1 and the cos of 90 is 0. If I'm understanding this correctly, as the latitude approaches +/- 90°, the distance in parsecs approaches 0.

_________________I am not expendable, I'm not stupid, and I'm not going.

Who is online

Users browsing this forum: No registered users and 0 guests

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum